1. Field of Invention
This application describes an improved fuel vapor storage canister of the type utilizing activated charcoal and includes pieces of foam rubber dispersed with the particles of charcoal in a manner so that the mixture is packed into the canister sufficiently that the foam is compressed whereby the particles of charcoal are tightly held together over long periods of time.
2. Description of the Related Art
Automobile fuel emission control systems have used fuel vapor storage canisters of the activated charcoal type for some time. Fuel vapors are collected and stored in the canister during certain periods such as when the vehicle is inoperative or when the vehicle's catalyst converter is too cool to effectively operate. The vapors are selectively directed to the combustion chamber for burning during other periods by drawing air from the atmosphere through the canister during what may be referred to as a purging operation.
Storage canisters filled with particles of activated charcoal are particularly effective in storing fuel vapors. The particles of charcoal are initially sized to be easily introduced into the canister but the particles are large enough so that they will not pass through the perforate walls of screens used in the canister to retain the charcoal. Even when the particles are of desired initial size, over time, the pack of charcoal particles settles and becomes loose. In response to the expected vibrations caused by the vehicle, this looseness allows the particles to rub against one another. The rubbings tends to reduce the size of the particles while ultimately the particle size approaches the configuration of dust. Such reduction in size is undesirable as the charcoal cannot be effectively retained in the canister and air has more difficulty passing through the pack of reduced size particles.
There are many patents which show charcoal type vapor storage canisters with solutions to the above identified problem of loose packing and particle reduction. The U.S. Pat. Nos. 4,683,862; 4,684,382; 4,714,485; 4,750,465 and 4,778,495 disclose this type of canister in which the particles of charcoal are packed into the canister against a thin member of foam material which may also act as a filter. A problem with all of these patents is that the thin foam pad is located remotely from much of the particles of charcoal and the volume of the tin pad is not very great to insure long term tight packing of the charcoal particles.
The U.S. Pat. No. 4,604,110 to Frazier discloses filter and odor adsorbing medium for removing odors from the air of a home or the like. The filter may be plastic foam and the odor adsorbing medium is a mixture of silica gel, activated carbon (charcoal) and zeolite. As in the patents discussed in the previous paragraph, the foam filter material may help to maintain the granular material tightly packed. However, the same limitations apply to this patent.